This invention relates in general to electronic brake control systems and in particular to an electro-hydraulic control unit for an electronic brake control system.
An Electronic Brake Control System (EBCS) is often included as standard equipment on new vehicles. When actuated, the EBCS is operative to modulate the pressure applied to the vehicle wheel brakes. A typical EBCS includes a plurality of solenoid valves mounted within a control valve body and connected to the vehicle hydraulic brake system between the brake master cylinder and the individual wheel brake cylinders. The solenoid valves usually are normally open, or isolation, valves and normally closed, or dump, valves. Proportional solenoid valves also can be included. The valve body further includes one or more accumulators for the temporary storage of brake fluid during an operating cycle of the EBCS.
A separate hydraulic source, such as a motor driven pump, is usually included in the EBCS. The pump supplies pressurized brake fluid for reapplying the controlled wheel brakes during an EBCS operational cycle. The pump is typically included within the control valve body while the pump motor is mounted upon the exterior of the control valve body. The pump motor is usually a direct current motor which operates from the vehicle power supply. Typically, the motor runs continuously during an EBCS braking cycle.
An EBCS further includes an electronic control module which has a microprocessor. The microprocessor is electrically connected to the pump motor, a plurality of solenoid coils associated with the solenoid valves, and wheel speed sensors for monitoring the speed and deceleration of the vehicle wheels. The microprocessor also is typically electrically connected to the brake light switch and receives a signal from the switch when the vehicle brakes are applied. Additionally, the EBCS may include one or more accelerometers which also are connected to the microprocessor. The microprocessor includes a memory portion which stores control algorithms for each mode of operation of the EBCS. The control algorithms comprise a set of instructions for the microprocessor which control the operation of the EBCS. The control module is usually mounted upon the valve body. The assembled valve body, motor and control module form a compact unit which is often referred to as an electro-hydraulic control unit.
During vehicle operation, the microprocessor in the EBCS control module continuously receives speed signals from the wheel speed sensors. Depending upon the received signals, the microprocessor can select one of several modes for operation of the EBCS. For example, if the microprocessor detects a potential wheel lock-up condition while the vehicle brakes are applied, the microprocessor will select an Anti-Lock Brake System (ABS) mode of operation and activate an ABS braking cycle. During an ABS braking cycle, the microprocessor actuates the pump motor and selectively operates the solenoid valves in the control valve to cyclically relieve and reapply hydraulic pressure to the wheel brakes. The hydraulic pressure applied to the wheel brakes is adjusted by the operation of the solenoid valves to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle as desired by the vehicle operator.
Another mode of operation provides Traction Control (TC). If the microprocessors detect excessive slip of a driven wheel when the wheel brakes are not applied, the EBCS will apply the brakes to the slipping wheel and thereby transfer more engine torque to the non-slipping wheel.
The EBCS can also include Vehicle Stability Control (VSC) mode of operation. The VSC mode is entered when the microprocessor detects a potential loss of directional control, such as, for example, a spin-out of the vehicle. In the VSC mode of operation, selected wheel brakes are applied to restore directional control of the vehicle.
This invention relates to an electro-hydraulic control unit for an electronic brake control system.
In the past electronic brake control systems have had rather bulky and heavy electro-hydraulic control units. Accordingly, the size can restrict the placement of the control unit within the vehicle while the weight adds to the total vehicle weight. Accordingly, it would be desirable to reduce the size and weight of the electro-hydraulic control unit.
The present invention contemplates an electro-hydraulic control unit for a hydraulic system that includes a valve body having a recess formed in a surface thereof. The recess is surrounded by a circumferential wall. A housing is removablely attached to the valve body wall and covers the recess. A circuit substrate is carried by the housing and extends over a portion of the valve body circumferential wall. At least one circuit component is mounted upon the circuit substrate and extends into the valve body recess.
The invention further contemplates that at least one solenoid valve is mounted upon the valve block and extends into the recess and that the circuit component mounted upon the substrate is a solenoid coil associated with the solenoid valve. Additionally, the circumferential wall includes at least one widened portion which is adjacent to the circuit substrate. The widened portion of the circumferential wall functions as a heat sink for an electronic component mounted upon the circuit substrate. To enhance the transfer of heat from the electronic component to the valve body wall, at least one via is formed through the circuit substrate between the electronic component and the widened portion of the circumferential wall. Additionally, a pad of heat conductive material can be disposed between the circuit substrate and the widened portion of the circumferential wall to further enhance the transfer of heat.
The invention also contemplates a pump motor mounted upon a surface of the valve body opposite from the surface that carries the housing. The motor has an electrical connector extending through a bore formed through the valve body and having an end which is received by an electrical motor connector mounted upon the circuit substrate. The motor connector mounted upon the circuit substrate extends into the recess formed in the valve body. In the preferred embodiment, the motor connector includes at least one electrical conductor overmolded with a body portion.
The control unit can be included in a vehicle brake system and utilized to provide anti-lock brake capability, traction control and/or vehicle stability control for the vehicle.